It has heretofore been reported mostly in Europe and the United States of America that isoflavone (soy isoflavone) contained in soybeans has prophylactic efficacies (antiestrogen effect) in breast cancer, carcinoma of the prostate, and other diseases and that it has alleviating efficacies (estrogenic-like effect) in climacteric and postmenopausal osteoporosis, hyperlipidemia, hypertension, etc. (H. Adlercreutz et al., (1992) Lancet, 339, 1233; H. Adlercreutz et al., (1992) Lancet, 342, 1209-1210; D. D. Baird et al., (1995) J. Clin. Endocrinol. Metab., 80, 1685-1690; A. L. Murkies et al., (1995) Maturitas., 21, 198-195; and D. Agnusdei et al., (1995) Bone and Mineral., 19 (Supple), S43-S48).
Recently, however, doubts have been cast on the clinical efficacy of soy isoflavone and, instead, it is reported that equol as the active metabolite of soy isoflavone is a key factor in the expected efficacies in clinical application. Thus, several reports are available arguing that in breast cancer, carcinoma of the prostate, and climacteric and postmenopausal osteoporosis, the efficacy of soy isoflavone is surpassed by that of equol, the metabolite of soy isoflavone (D. Ingram et al., (1997) Lancet, 350, 990-994; A. M. Duncan et al., (2000) Cancer Epidemiology, Biomarkers & Prevention, 9, 581-586; C. Atkinson et al., (2002) J. Nutr., 32(3), 595S; H. Akaza et al., (2002) Jpn. J. Clin. Oncol., 32(8), 296-300; and S. Uchiyama et al., (2001) Ann. Nutr. Metab., 45, 113(abs)).
Moreover, many lectures were delivered on the subject of equol in the 4th International Symposium on the Role of Soy in Preventing and Treating Chronic Disease (San Diego, USA, 2001), and in December 2002 a comprehensive review of studies on equol was also reported. Thus, it is getting more or more accepted in academic circles that equol is the very entity of efficacies of soy isoflavone (K. D. R. Settchell et al., (2002) J. Nutr., 132, 3577-3584).
Futhermore, compared with soy isoflavone, equol is delivered to tissues such as the breast tissue and prostatic tissue with by far greater efficiency and, from this fact, the physiological significance of equol is endorsed (J. Maubach et al., (2003) J. Chromatography B., 784, 137-144; T. E. Hedlund et al., (2003) The Prostate, 154, 68-78).
Equol is produced by the intestinal flora and the involvement of individual difference in its production has been reported. It is also reported that equol producers among the Japanese account for about 50% (S. Uchiyama et al., (2001) Ann. Nutr. Metab., 45, 113 (abs)). Individuals who cannot produce equol are suspected to be lacking in equol-producing bacteria in their intestine. In such individuals, it is suspected that the expected antiestrogen and estrogenic-like effects may not be expected even if processed soybean foods are ingested. In order that the expected effects may be expressed in such individuals, it seems to be a reasonable course of action to have them ingest equol-producing bacteria or equol as such.
Based on the above idea, the inventors had conducted intensive investigations and isolated from human stools novel 3 strains of microorganisms and identified them: namely Bacterioides E-23-15 (FERM BP-6435), Streptococcus E-23-17 (FERM BP-6436), and Streptococcus A6G225 (FERM BP-6437), as equol producing-bacteria suitable for the expression of said antiestrogen and estrogenic-like effects, among other effects, and applied for a patent claiming inventions concerning these equol-producing strains of microorganisms and utilization of the microorganisms (WO99/07392).